Hydraulically controlled air leg structure



Sept. 22, 1964 J, HLN-TER ETAL 3,149,541

` HYDRAULICALLY CONTROLLED AIR LEG STRUCTURE y I 5 Sheets-Sheet 1 FiledJuly 12, 1963 ATTORNEY sept. 22, 1964 3,149,541

HYDRAULCALLY CONTROLLED AIR LEG STRUCTURE J. F. HUTTER ET AL 5Sheets-Sheet 2 Filed July l2, 1965 PATENT AGENT Spt. 22, 1964 J. F.HUTTER ET AL 3,149,541

HYDRAULICALLY CONTROLLED AIR LEG STRUCTURE Filed July l2, 1965 5lSheets-Sheet I5 QN com. Nm@ mmm J www www uw (uw .N QN mmm o mm.

NNN @N mb N .llink PATENT AGENT Sept 22, 1964 J. F` HUTTl-:R ET ALHYDRAULICALLY CONTROLLED AIR LEG STRUCTURE 5 Sheets-Sheena?I 4 FiledJuly l2, 1963 Num@ PATENT AGENT J. F. HUTTER ET A L v3,149,541

5 Sl'xeetsf-S'heetv 5 T TOR BATNT AGENT Sept. 22, 1964 HYDRAULICALLY'CONTROLLED AIR LEG STRUCTURE Filed July 12, 1963' United StatesPatent() 3,149,541 HYDRAUMCALLY CUNTROLLED All( LEG STRUCTURE Karnes F.Hutter and Leonard Kelly, Bancroft, Ontario, Canada, assignors to K d: HEquipment Limited, Toronto, ntario, Canada Filed `lruly 12, 1963, Ser.No. 295,298 1'7 Claims. (Cl. 91--422) This invention relates to fluidpower actuators and, more particularly, to a hydraulically controlledair leg structure. This application is a continuation-in-part ofcopending application Serial Number 165,397, tiled January 10, 1962, nowabandoned.

Long-stroke air cylinders or air or pusher legs are quite generally usedto support and position rock drills, and supply the considerable forcerequired for effective rock comminution by the percussive drill. Indrifting or crosscutting, holes are drilled horizontally in a presentpattern into the face for loading and blasting. The horizontal pressureand upward supporting force is supplied by an air leg, the piston ofwhich is attached to the machine and may swivel in a vertical plane,while the cylinder itself slants backwards and downwards to a spike-liketermination which is driven into the floor of the drift.

Apart from the difficulty of initially lining up the holes because oflack of precise control, there is a continual danger of the drill steelbreaking once the hole is established and heavy pressure is beingapplied. Drill steel is subject to constant flexing and hammering, andeventually fatigues, fracturing suddenly. Relieved of restraint, the airleg explodes under full line pressure, pulling the drill operatortowards the face and possible impalernent on the broken drill steel,unless his reactions are fast enough to Vrelease his grip on themachine.

lt is an object of this invention to provide an air leg structure whichis subject to safe, convenient, controllable operation, and which has anincreased effective life.

The invention will be described with reference to the accompanyingdrawing, in which FGURE l is a sectional side elevation of an air legincorporating the structure of the present invention,

FlGURE 2 is a sectional side elevation of a modified forni of air legstructure,

FIGURE 3 is a sectional side elevation of a further modification of airleg stucture,

FIGURE 4 is an enlarged sectional elevation of a valve assembly employedin the modification of FIGURE 3,

FIGURE 5 is a sectional elevation of a modified form .of the valveassembly shown in FGURE 4,

FiGURE 6 is a sectional side elevation of another modified form of airleg structure, and

FIGURES 7 and 8 are sectional side elevations of additionalmodifications of air leg structures.

Referring to FIGURE l, a main air cylinder barrel 117 is terminated atone end by a blind end cap 118 in which an external ground spike 119 isscrewed. A rod end cap 121i is screwed into the other end and forms thebearing through which a tubular air piston rod 121 extends andreti-acts, sealed by O-rin gs as shown and including a molded-rubber rodend wiper 122.

A standard rock drill fitting 123 is screwed into the external end oftubular air piston rod 121, and includes an air inlet and exhaustorifice 124, together with pressure Iand relief valves and swivelattachment to the rod drill (not shown). An air piston 125 is a pressurefit on the internal end of air piston rod 121, and slides in cylinderbarrel 117 on O-ring seals as shown.

A tubular hydraulic piston rod 126 is screwed into blind end cap 118 andlocked by a nut 127. Air piston 125 is centrally drilled, as shown, toallow sliding movement along hydraulic piston rod 126, and O-rings 1283,149,541 Patented Sept. 22, 1964 ICC provide seal and wiping action.The other end of piston rod 12d-is terminated by a hydraulic piston seat129. A hydraulic piston is held in contact with seat 129 by a lightpiston spring 131 reacting against a set collar 132 which is secured topiston rod 126.

An air transfer tube 133 is free to slide in tubular hydraulic pistonrod 126 and through a central drilling in hydraulic piston seat 129,which is provided with O-ring seal 134. Transfer tube 133 is brazed to afloating oil reservoir cover 135 which may slide in tubular air pistonrod 121 on O-ring seal, as shown. The arrangement described provides arear oil chamber 136 in piston rod 121 between pistons 125 and 130 and aforward oil chamber 137 between piston 13G and cover 135. A bleederpassage 13351 closed by a plug 138 is provided as an air bleed whenfilling rear oil chamber 136 and forward oil chamber 137 with oil. Asealed air passage is thus provided from the external supply via orifice124 into an air inlet chamber 139 in piston rod 121 thence throughtransfer tube 133 into tubular hydraulic piston rod 126, and finally outof an orifice 140 in blined end cap 118 into main air pressure chamber141 in main cylinder 117 between cap 118 and piston 125.

A controlled air passageway is provided in piston 125 from main airpressure chamber 141 to forward air chamber 142 in the main cylinderforwardly of piston 125. This passageway is provided by a shuttle valvearrange- 'ment in piston 125 and comprising an exhaust shuttle valve 143slidingly mounted in a valve liner 144 fixed in a hole 145 drilled inthe pressure chamber side of piston 125. A port 146 providescommunication from the hole 145 to the chamber 142. A spring 147 urgesvalve 143 in one direction against a snap retaining ring 148 in liner fthrough transfer ports 149 formed in the valve via a transfer chamber15d formed in hole 145 into transfer port 146.

Movement of valve 143 in the other direction is limited by a valve seat.51 provided in hole 145. It will be apparent that the valve 143 may beforced by air pressure Aagainst seat 151, thus breaking the connectionbetween main pressure chamber 141 and forward air chamber 142.

A relief port 152 is provided in rod end cap 128 to connect forward airchamber 142 with a low pressure relief valve 153. A handle 154 isprovided for moving and positioning the air leg.

The action of the air leg described is as follows:

Assume first that the air leg is in its fully retracted position, thenair piston 125 is close to blind end cap 118, shuttle valve 143 is heldagainst retaining ring 148 by spring 147, rear oil chamber 136 is at itsmaximum Volume, forward oil chamber 137 is at its minimum volume withhydraulic piston seat 129 located close to fioating oil reservoir cover135, air inlet chamber 139 is at its minimium value, and low pressurerelief valve 153 is closed.

If now compressed air is admitted at inlet 124, it is transmittedthrough transfer tube 133 and orifice 148 of hydraulic piston rod 126,into air pressure chamber 141. Orifice 141) is considerably larger thanshuttle valve transfer ports 149, and furthermore, forward air chamber142 is relieved at a few pounds above atmosphere by relief valve 153,consequently shuttle valve 143 closes against seat 161 when thedifferential pressure on opposite faces of the shuttle valve reach acertain value determined by spring 147.

The air pressure against the face of piston 125 tends to move it awayfrom blind end cover 118, extending air piston rod 121 from thecylinder, However, the speed of movement is limited by the speed withwhich the pressurized oil in rear oil chamber 136 can leak past apredetermined clearance provided between piston 130 and the bore inpiston rod 121. It will be apparent that a sealed piston with aninternal leak orifice would be an alternative arrangement.

` As the piston rod 121 extends and hydraulic piston rod 126 iswithdrawn from rear oil chamber 136, there is a net movement ofreservoir cover 135 away from rock drill fitting 123 to compensate forthe volume difference between piston rod 126 and air transfer tube 133.On this extension stroke, air is forced out of forward air chamber 142through relief valve 153.

It is important to realize that it is very undesirable, in an atmosphereof abrasive rock dust, to allow outside air to be drawn anywhere intothe cylinder on the retraction stroke, although this is common practice.A controlled air leak through the air piston may be used in an attemptto overcome this disadvantage but this is wasteful of air power. Thecombination of shuttle valve and low pressure relief valve in thearrangement described substantially eliminates dust contamination andair waste.

The action on retraction will now be described with orifice 124exhausted to atmosphere through an external valve (not shown) under thecontrol of the rock drill operator. As the pressure in main pressurechamber 141 drops to a certain pressure determined by spring 147,shuttle valve 143 opens, allowing the air to exhaust through port 146into forward air chamber 142 as well as through orice 140. In thismanner, no opposition is offered to the normal gravity retraction of theair piston by any vacuum effect in forward air chamber 142, and no airis drawn in from outside. At the same time, the expansion of rear oilchamber 136 behind hydraulic piston 130, lifts piston 131) off seat 129against light spring 131, allowing oil to ow freely from forward oilchamber 137 as required, putting virtually no compressive force onhydraulic piston 130. Floating end cover 135 responds to the retractionstroke by moving towards rock drill fitting V123, as a consequence ofthe hydraulic piston rod moving into the rear oil chamber and replacingthe effect of smaller diameter air transfer tube 133.

The safe controlled maximum speed of extension of this hydraulicallycontrolled air leg is of major significance from the point of view ofsafety and convenience. However, an additional advantage derives fromthe full sealing provided in the structure described. The mechanism iscompletely isolated from the water and dust contaminated air, and, freeof abrasion particles, the seals last their full rate life. This is manytimes greater than the life of seals working in the degrading conditionspresent in heretofore employed drill air legs.

Furthermore, inv this hydraulically controlled air leg, the highfrequency vibrations caused by the percussive nature of the drill aresubstantially oil-damped, and taken up at the swivel joint rather thanby movement of the air piston. This high frequency movement of thepiston in the dust-contaminated cylinder of a standard air leg is thecause of the very high rate of wear in the leather seals employed. ThisWear is so rapid that it is common practice to provide the miner withspare seals which he may change himself during the shift, at no smallcost in downtime.

FIGURE 2 illustrates an air leg structure which permits rapid retractionof the main piston rod, if required. The main air cylinder barrel isindicated at 229 and is provided at one end with a blind end cap 230 andat the other end with a rod end cap 231. The cap 231 includes a sleeve232 having a liner 233 and seal 234 through which extends a tubular airpiston rod 235. An air piston 236 is mounted on the end of rod 235 andslides in barrel 229 on a sealing ring 237.

A tubular hydraulic piston rod 238 has one end fixed to blind end cap230 and a hydraulic piston seat member V239 fixed to its other end. Anair transfer tube 240 is free to slide in piston rod 238 and throughmember 239 which is provided with a sealing ring 241. Transfer tube 249is fixed to a fioating oil reservoir cover 242 which may slide in airpiston rod 235 on sealing ring 243.

A hydraulic piston 244 is slidingly mounted on piston rod 23S and, inconjunction with piston seat member 239, provides controlledcommunication between a rear oil chamber 245 in piston rod 235 and aforward oil chamber 246 in piston rod 235. Piston 244 has a closedposition wherein it is in engagement with valve seat member 239 and anopen position defined by engagement with retaining ring 247 on pistonrod 23S wherein communication between chambers 245 and 246 is providedthrough ports 248 and annular passage 249 in piston 244.

It will be apparent that in barrel 229 there is provided, by piston 236,a main air chamber 250 rearwardly thereof and a forward air chamber 251forwardly thereof. Communication between air inlet chamber 252 forwardlyof cover 242 and main air chamber 250 is provided through transfer tube24?, hollow piston rod 238, and ports 253 in rod 238.

Controlled communication between chambers 25) and 251 is provided by anannular interior air transfer passage 254 surrounding piston rod 238 inthe rearward end portion of piston 236, an annular exterior recess 255in piston 236 adjoining the forward end thereof and forming an annularpassage 256, and a plurality of radially extending ports 257 connectingsuch passages 254 and 256 through a bore 258 in the piston 236. Slidablymounted in bore 258 and on piston rod 238 is a cylindrical valve 259having sealing rings 260, 261. Bore 258 terminates in an annularshoulder 262 adjoining passage 254, such shoulder constituting a valveseat engageable by valve 259 to define the closed position thereof andwherein ports 257 are closed.

It will be observed that valve 259 controls the passageway between mainair chamber 250 and forward air chamber 251 in response to thedifferential pressure between rear oil chamber 245 and main air chamber250.

The compressed air admitted to the air piston rod 235 through theconventionaly provided control valve (not shown) transmits pressurealmost instantaneously to the hydraulic fluid through the oatingreservoir cover 242. Corresponding build-up or reduction of pressure inmain air chamber 250 lags the controlled pressure because of therestrictive nature of the air transfer tube 240 and the capacity of themain air chamber 256.

Thus, when feed pressure -is applied, valve 259 closes against valveseat 262 and the pressure then builds up in main air chamber 250,extending the air leg. Once rvalve 259 is closed, ythe face area thereofexposed to the air presure in annular transfer passage 254 becomessmaller than the area exposed to the hydraulic pressure in chamber andthe valve becomes overbalanced. Control air pressure on the hydraulicfluid must be reduced below the pressure in main air chamber 25@ beforevalve 259 will re-open, and again the restriction of transfer tube 240and the capacity of chamber 2511 assists the speedy attainment of thisrequired opening differential.

Once valve 259 shuttles open in response to a sharp reduction in controlpressure, air in chamber 259 may exhaust freely through ports 257 intoforward air chamber 251 which may be ported directly to atmosphere, asindicated at 263, or held at slight positive pressure by low pressurerelief va-lves such as indicated at 153 in FIG- URE l. This rapidreduction in the pressure of main air chamber 250 allows rapidretraction of the main air piston rod 235 if required, or simply rapidpressure relief tosome intermediate control pressure since it will beobserved that valve 259 will close whenever the pressure in chamber 251has dropped to the set control pressure.

It will be apparent that the air pressure in inlet chamber 252 istransmitted almost instantaneously to the hydraulic fluid and that thispressure is virtually independent of the pressure/how conditions in theair chambers of the device itself. By using this hydraulic pressure toactuate the relief transfer valve 259 with high flow characteristic inthe air piston, retraction can be accomplished with speed and ease.

There is also illustrated in FGURE 2, an improved blind end coverattachment. It is common prac-tice to secure the blind end cover to thecylinder barrel by screw threads. This is not entirely satisfactorybecause the cylinder barrel must be ordinarily of light metal, such asaluminum alloy, and all the hammering of the drill is transmittedthrough the threaded connection to the ground spike. Loosening of theblind end cap and destruction of the threads, with consequent scrappingof valuable tubing, is a common mishap.

As shown, the blind end cover 230 comprises anend member 25d having arecessed annular shoulder 265 engageable with the end of the barrel 229,and a compression plug 266 screw-threadedly mounted in a socket 267 inmember 264 and having a sliding fit in the cylinder barrel 229. Plug 266has an outer annular recess 268 and disposed in such recess is acompression collar 269, which is slidable on the plug within barrel 229but is restrained from backward movement by a retaining ring 270 mountedin the barrel. A plurality of sealing rings 271, such as conventionalC-rings are interposed ia recess 268 between the compression collar 26%and a shoulder 272 defining the termin-ation of the recess.

The rings 271i. provide a pressure sea-l and result in a vibration-prooflock washer effect by maintaining tension on the threads over severalrevolutions of the linal tightening of the cover member 26d. Shoulder1F35 is under constant pressure against the end face of the cylinderbarrel, and vibration is transmitted without wear, loosening, or hammer.

Further embodiments of 4the invention will now be described withparticular reference to air legs incorporating power retraction means.

When drilling horizontally with an air leg/drill combination, it isnecessary for the operator to regularly advance the air leg, as thedrill steel feeds into the rock, in order to maintain the correct angleand force components for optimum drilling. When non-retractable air legsare used, the feed pressure must be turned off, and the air leg pulledup and positioned manually each time a move is made.

Retractable air legs now in use are generally of the upside-down type,i.e., the cylinder is attached `to the drill, and the piston rod endpresses against the sill. This orientation simplifies the positioning ofthe usual four-way extend/ retract valve, which should be at the blindend of the air leg cylinder to facilitate the plumbing to the front andrear air chambers, and must also be conveniently in reach of theoperators hand on the drill. However, this inverted orientation has adisadvantage in that the elevation of the handle on the cylinder changesas the air leg extends, and while the power retraction does reduce thelift required, nevertheless, the leg must be guided and positionedmanually. n high back holes, the handle m-ay be at chest level, which isnot a convenient height for lifting.

Two versions of a right-way-up retractable air leg, incorporatinghydraulic damping and a single valve control of extend-retract andpressure regulation, will now be described.

Referring to FGURES 3 and 4, 27?) is a main air cylinder barrelterminated at one end by a blind end cap 274i in which an externalground spike may be screwed. A rod end cap 275 is screwed onto the otherend and supports a bearing 276 through which a tubular air piston rod277 extends and rctracts. As shown, the bearing includes a replaceableliner 278, a rod end wiper 279, and a sealing O-ring 288.

It will be apparent that a standard rock drill fitting will be screwedonto the external end 281 of the piston rod 277, to connect the air legto a drill, and to provide an air passageway into the piston rod 277from the pressure control valve (not shown).

An air piston 282 is a tight screw lit on the internal end of air pistonrod 277 and slides in the cylinder barrel 273 on O-ring seal 283, asshown.

One end of a tubular hydraulic piston rod 284 is screwed into a retainer285 carried by a valve body 286 fixed to blind end cap 274i. Air piston282 is centrally drilled at 287 to allow sliding movement along pistonrod 284, an O-ring hydraulic seal 288 being provided. A hydraulic pistonseat member 289 is mounted on the other end of piston rod 284. Ahydraulic piston 290, slidable on .piston rod 28d, has a limited travelbetween a retaining ring 291 on the rod 284 and the seat 289. Hydraulicpiston 29@ provides controlled communica-tion between rear oil chamber292 and forward oil chamber 293 in piston rod 277. When piston 29d is inengagement with seat 289 (as during extension of the air leg) there iscontrolled oil transfer between chambers 292 and 293 through an annularpassage 2% in piston 290, a port 285 in piston 298 leading from chamber292 to passage 284, and selfcleaning grooves 296 on the sealing face ofpiston 290. When piston 298 moves off seat 289, oil flow in the oppositedirection is unrestricted through passage 294 and port 295 (as aretraction of the air leg).

An air transfer tube 2427 is free to slide in tubular hydraulic pistonrod 284 and through a central drilling 298 in piston seat 289, which isprovided with a sealing ring 229. A floating oil reservoir cover 380 isfixed to the forward end of transfer tube 297. Cover 300 is slidable inair piston rod 277 on sealing ring Stil.

Referring now more particularly to` FIGURE 4, valve body 286 houses apressure sensitive four-way valve structure now to be described.

As shown, hydraulic piston rod retainer 285, which is provided with aseal 382, is retained in body 28d by means of a ring 283. Also mountedin the body between retainer 285 and a retaining ring 3nd is a valveliner 36S. Also mounted in the body between retaining ring 384 andanother retaining ring 386 are a pair of spring housings 387 containinga spring 308, housings 307 being normally spaced apart under theinfluence of spring 308.

A shuttle valve member 369 is mounted in liner 385. Valve member 309 hashas a pressure distribution chamber 315.8. Chamber Sill) has a port Sillleading to its forward face adjacent retainer 285, and communicatingwith the interior of piston rod 284 through opening 312 in retainer 285.Port 311 is normally closed by a check valve 313 under influence of aspring 31d. Chamber 3l@ has a small orifice Silla bypassing check valve313.

An extension port 315 connects chamber Sill with a circumferentialgroove 326 in member 389 and a retraction port 3l7 connects chamber 318with a circumferential groove SiS.

Member 389 also contains an exhaust passage 319 which is open rearwardlythereofV and which has a port 320 connecting with a circumferentialexhaust groove 321 in member 389. Rings 322 provide pressure sealsbetween the circumferential grooves, as shown.

Liner 385 has `a plurality of radially extending ports 323 leadinginwardly from a circumferential extension groove 324 thereon andcommunicating with groove 321 Liner 395 also has a plurality of radiallyextending ports 325 leading inwardly from a circumferential retractiongroove 326 thereon iand communicating with groove 318. Liner groove 32dcommunicates with extension ports 327 in valve body 286 and liner groove326 communicates with retraction ports 328 in valve body 286.

A circumferential groove 329 in valve body 286 provides a passagewayfrom retraction ports 32S to an eX- ternal transfer tube 33d whichcommunicates with the forward air chamber 331 of the air leg through anannular recess 332 in the piston 282. Extension ports 327, separated bya sealing ring 333 from the retraction groove 329, lead directly intothe main air chamber 334 via a circumferential recess 33S in body 285.

Preferably, the liner 3695 is formed of a plastic composition such asthat known under the trade name Teflonamas-r1 The circumferentialgrooves 324 and 326 therein are sealed by O-rings 336. Danger of O-ringdamage or extrusion may be obviated by making the diameter of the @-ringgreater than that of the ports 323 and 325.

Exhaust passage 319 communicates with atmosphere through openings 337 inspring housings 367, a space 338 between valve body 286 and the blindend cover 274, and ports 339 in the blind end cover.

The parts as shown inthe drawing are in their normal or retractposition.

In operation, when it is desired to extend the air leg, air underpressure is admitted through air transfer tube 297 'and piston rod 28dto the forward end of valve member 309 and when the air pressureoverbalances the force exerted by spring 308, valve member 309 will moverearwardly to its extend position. In this position, air under pressureis supplied to main air chamber 334i through elements 311, 315, 316,323, 327 and 335, while forward air chamber 331 is exhausted to`atmosphere through elements 332, 339, 329, 325 and 321, to the ports339.

If it is required to reduce the pressure of extension, this may be doneby slowly backing off control pressure and relieving through by-pass311:1.

On the other hand, if a quick relief of pressure is required to switchvalve 309 to retraction position, the standard manual control valve maybe closed rapidly. Check valve 313 then permits quick exhaust ofpressure in hydraulic piston rod 234, valve 309 switches to retractposition, and the large capacity of main air chamber 33d exhaustsquickly through elements 323, 321, 32% and 319 and thence to ports 339.Thus, the check valve by-pass arrangement permits a rapid switch toretraction position, without waiting for the large capacity of the mainair chamber 334 to bleed down to the switchover pressure. It will berecognized, however, that while the check valve is of substantialconvenience, it is not essential to the fundamental operation.

The setting of the valve mechanism described may be such that powerretraction occurs at pressures between say, to 30 p.s.i. Above, say, 30p.s.i., the valve member 309 shuttles, exhausts the forward air chamber331, and pressurizes the main air chamber 334 for rod extension atwhatever pressure is set by means of the usual manual control valve.

Referring now to FIGURE 5, a valve arrangement is shown which permitsuse of a greater range of pressures in both the extension and retractionoperations.

The embodiment of FIGURE 5 is substantially the same as that of FIGURES3 and 4 but includes the provision of ball detents 356 mounted in valvebody 236, and urged by springs 341 into engagement with the side wall ofthe forward spring housing 3137. The latter housing has acircumferential groove 342 therein arranged to receive the spring-loadeddetents 340 when the housing is moved to extend position by the valvemember 309.

By `appropriate choice of spring pressure and detent breakaway force, aWide choice of overlapping extension and retraction ranges is available.Thus, the control valve 309 may be set to shuttle to extend position ata pressure greater than, say, 60 p.s.i., and the detents may be employedto hold it in this position until the pressure is reduced to, say,p.s.i., when it will flip back to retract position. Thus, once aparticular extension mode has been selected, any pressure between l0p.s.i., and full line pressure may be used for extension. Similarly,once the pressure is reduced below l0 p.s.i., any pressure between zeroand 60 p.s.i., may be selected for retraction.

Briey, therefore, Valve return spring 308 determines the controlpressure required to switch the valve to extend position, while thedifference between the force of spring 358 and the detent restrainingforce, determines the switching pressure below which the valve willshuttle back to retrac position.

FIGURE 6 illustrates a further modilication of ahydraulically-controlled power-retractable air leg. It includes a mainair cylinder barrel 343, a tubular air piston rod 344 extending slidablythrough a rod end cover 345, an air piston 345 fixed to the inner end ofrod 344 and forming in barrel 343 a main air chamber 347 and a forwardair chamber 343, and a tubular hydraulic piston rod 349 having one endxed to a blind end cover element 35u and a hydraulic piston 351 slidablymounted thereon between retaining ring 352 and piston seat 353 fixed toits other end. An air transfer tube 354 extending into hydraulic pistonrod 349 and carrying a floating oil reservoir cover 355 providescommunication between air inlet chamber 356 and main air chamber 347through port 357. A drill titting 358 is connected to the forward end ofair piston rod 344.

A thin-walled tube 359 is concentrically mounted within the air pistonrod 3454 in radially spaced relation to the rod 344 and to the hydraulicpiston rod 349. The rearward end of tube 359 extends into air piston 346and is provided with a seal 35@ to seal the rear oil chamber 361 from anannular air passageway 362 formed between the tube and the air pistonrod 344. The forward end of tube 359 is mounted on a boss 363 on tting353 and is retained thereon by a retaining ring 364.

The passageway 362 connects the forward air chamber343 through port 365with a retraction control port 356 in fitting 358. An extension controlport 367 in fitting 353 communicates with air inlet chamber 356 and mainair chamber 347 through the transfer tube 354 and hydraulic piston rod349. The ports 366 and 367 will be connected to conventional controlvalve mechamsm.

Communication between rear oil chamber 361 and forward oil chamber 368in tube 359 is freely established in the retracted position of the airleg in which position piston 351 is spaced from seat 353, through anannular passageway 369 in piston 351 having ports 37d communicating withchamber 361 and the annular space 371 between seat 353 and the bore oftube 359. As piston rod 344 extends, piston 351 will tend to engage seat353 to close passageway 369. Thereafter, the speed of movement of thepiston rod is limited by the speed with which the pressurized oil inrear oil chamber 361 can leak past the meeting faces of piston 351 andseat 353. As in respect of FIGURE 3, one of these meeting faces may beprovided with grooves such as 236.

It will be observed that the air leg modifications set forth herein havebeen described in relation to that orientation thereof wherein air isadmitted through the piston rod and the blind end of the cylinder is tothe ground. It will be apparent that the reverse orientation of the airlegs may be provided by making minor obvious rearrangements of the partsthereof if such orientation were necessary or preferred.

FIGURE 7 illustrates a form of the invention as applied to a pusher leg.The main tube or cylinder is indicated at 372 and is provided at one endwith a blind end cap 373 and spike 374 and at the other end with a glandnut 375. A hollow push rod or air piston rod 376 extends through thegland nut into the cylinder and is provided with an air piston 377 fixedto its inner end and a suitable adaptor 378 on its outer end. The pistonmay be provided with a packer ring 379 engaging the inner wall of thecylinder.

Located within the air iston rod 376 is a floating hydraulic cartridge335 comprising a tube 351 each end of which terminates inwardly of butclosely adjacent the adjoining end or" the rod 376. The externaldiameter of the tube 331 is less than the internal diameter of rod 376to provide a space 382 between the opposed wall surfaces of rod 376 andtube 381. As shown, the radial extent of space 332 may be relativelysmall. The inner end of tube 331 is closed by a sealing cover 333 havinga portion extending into the tube provided with an O-ring 384. Cover 383also has a portion extending outside 9 the tube, the end of which bearson a washer 385 Which in turn is seated on a ring 386 fixed within theend of rod 376.

The other end of tube 331 is closed by a floating reser- Voir cover 387which extends into the tube and is provided with an O-ring seal 338. Anair bleed passage 389 in the cover 337 is closed by a plug 3%. A spring391 is interposed between the end of tube 331 and adapter 37S. Thespring holds the cartridge assembly in place while permitting it tofloat. It eliminates any need for close tolerances on the tube lengthand prevents cartridge hammer during drilling operation.

A hydraulic piston rod 392 has one end fixed to blind end cap 373 andextends axially into piston rod 376 and tube 381. The rod 392 extendsthrough cover 383, sealing means 393 therewith being provided. Mountedon the free end of piston rod 392 within tube 381 is a piston assembly394 incorporating valve means operable during the extension andretraction strokes of the piston rod 376. The assembly 394 comprises aretraction valve member 395 and an extension valve member 395 each inthe form of a collar fixed to the rod 332, and a tubular valve seatmember 397 freely reciprocal between members 395 and 3%. Member 397 hasan axial fiuid flow passage 397e therein and has sealing engagement, bymeans of seal 39717, with tube 381. Member 397 has, as shown, a bevelledseat 398 and one end for engagement with a complementary seat 399 onmember 395 and a bevelled seat 4h@ at its other end for engagement witha complementary seat 491 on member 396. Member 3% has a relatively largeslot or passage 402 therein which provides relatively unrestricted fluidflow therethrough during the retraction stroke, i.e., when member 397 isseated on member 395. Member 396 has a relatively smaller slot orpassage 4l3 therein which provides controlled fluid flow therethroughduring the extension stroke, i.e., when member 397 is seated on member3%.

Air is supplied to the cylinder through an orifice 404 in adapter 37thence through space 382 into an outer annular recess 4% in cover 383,ports 4416 and inner annular recess 407 in cover 383, central opening408 in washer 335, and finally through ring 3% into main air pressurechamber 469. Flow of air out of forward air chamber 41h is around aspacer 411 (which may be provided as required) and through a groove 412,annular space 413, and ports 414 in the gland nut 375.

The cartridge tube 424 is filled with oil, in operation, and it will beapparent, as previously indicated, that, during the extension stroke ofpiston rod 376, restricted flow of oil through passage 493 occurs fromthe chamber on one side of the piston assembly 394 to the chamber on theother side of the piston assembly. During the retraction stroke,unrestricted flow of oil through passage 4&2 from one chamber to theother occurs.

The pusher leg described is a simplified and less expensive version ofthe invention in that it does not provide for power retraction. Thissingle-acting leg eliminates the need for expensive honing.

FIGURE 8 shows an adaptation of the structure of FIG- URE 7 for use as astopper. Main cylinder 415 is shown as mounted on a conventional stopperbody 416. Holland push rod or air piston rod 417 extends through bearing41% in the outer end of the cylinder. A plate 419 closes the inner endof the cylinder and provides an air inlet chamber 42@ adjacent thestopper body. A foot 421 closes the outer end of rod 417 and an airpiston 422 is mounted on the inner end within the cylinder.

A hydraulic cartridge 423, adapted to receive a supply of oil, isdisposed within the hollow piston rod 417 and comprises a tube 424,cover 425 closing the inner end thereof and floating reservoir cover 426closing the outer end thereof, and positioning and retaining spring 427.The cartridge provides an air space 428 between its external wall andthe internal wall of the rod 417. Cover 425 bears upon a collar 429 inrod 417.

A hydraulic piston rod 43? has one end fixed to plate l@ 419, as by nuts431 and 432, and extends axially into tube 424 through cover 425. Apiston assembly 433 similar to piston assembly 394 is mounted on pistonrod 429 within tube 424.

Chamber 42d has an air inlet 434 leading from a control valVe (notshown) and air flow is from chamber 420 through port 43S in plate 419,and into the end of piston rod 417 to move piston 422 and extend therod. Air also flows through collar 42@ and space 428 to the outer endportion of the piston rod to permit axial movement of the floatingreservoir cover 426 The operation of the device will be apparent fromthe foregoing description. Air is supplied, as described, to effect theextension stroke. For retraction, air transfers through the unsealedclearance of bearing 413 and piston rod 417.

We claim:

l. A hydraulically controlled air leg comprising a main cylinder barrel,an air piston rod extending axially into said barrel and having rear andforward hydraulic fluid chambers therein, an air piston fixed to saidpiston rod in said barrel, a hydraulic piston rod axially arranged insaid barrel and fixedly connected thereto, said hydraulic piston rodextending through said air piston, a floating cover in said air pistonrod defining one end of said forward hydraulic fluid chamber, ahydraulic piston on said hydraulic piston rod, said hydraulic pistonseparating said rear and forward hydraulic fluid chambers, and meansproviding an oil flow passage through said hydraulic piston from one ofsaid chambers to the other.

2. A hydraulically controlled air leg as defined in claim 1, including ahydraulic piston seat fixed -to said hydraulic piston rod, saidhydraulic piston having a first position defined by engagement thereofwith said seat and a second position defined by disengagement thereofwith said seat, means forming a restricted passageway leading from oneof said chambers to the other through said hydraulic piston and saidseat in said first position.

3. A hydraulically controlled air leg comprising a main cylinder barrel,an air piston rod extending axially into said barrel and having rear andforward hydraulic fluid chambers therein, an air piston fixed to saidpiston rod in said barrel, a hydraulic piston rod fixed to and axiallyarranged in said barrel, said hydraulic piston rod extending throughsaid air piston, a floating cover in said air piston rod defining oneend of said forward hydraulic fluid chamber, a hydraulic piston on saidhydraulic piston yrod and having limited axial movement thereon, saidhydraulic piston separating said rear and forward hydraulic fluidchambers, means providing an oil flow passage through said hydraulicpisten from one of said chambers to the other, and means controllingfluid flow through said passage.

4. A hydraulically controlled air leg as defined in claim 1, including ahydraulic piston seat fixed to said hydraulic piston rod, said hydraulicpiston having a first position dened by engagement thereof with saidseat and a second position defined by disengagement thereof with saidseat, means forming a restricted passageway leading from one of saidchambers to the other through said hydraulic piston and said seat insaid first position, said chambers being in substantially unrestrictedcommunication with each other in said second position.

5. A hydraulically controlled air leg comprising a main air cylinderba-rrel having a blind end cap at one end thereof and a rod end cap atthe other end thereof, a tubular air piston rod extending through saidrod end cap into said barrel, an air piston fixed to said piston rod insaid barrel, a hydraulic piston rod axially arranged in said air pistonrod and having one end fixed to said blind end cap, a floating oilchamber cover in said air piston rod, a hydraulic piston on saidhydraulic piston rod between said oil chamber cover and said air piston,said air piston rod having therein a rear oil chamber between saidhydraulic piston and said air piston and a forward oil chamber betweensaid hydraulic piston and said oil 'l l chamber cover, and meansproviding an oil flow passage from one of said chambers to the other.

6. A hydraulically controlled air leg comprising a main air cylinderbarrel having a blind end cap at one end thereof and a rod end cap atthe other end thereof, a tubular air piston rod extending through saidrod end cap into said barrel, an air piston fixed to said piston rod insaid barrel, a hydraulic piston rod axially arranged in said air pistonrod and having one end fixed to said blind end cap, a floating oilchamber cover in said air piston rod, a hydraulic piston on saidhydraulic piston rod between said oil chamber cover and said air piston,said air piston rod having therein a rear oil chamber be- -tween saidhydraulic piston and said air piston and a forward oil chamber betweensaid hydraulic piston and said oil chamber cover, means providing an oiliiow passage from one of said chambers to the other, and meanscontrolling oil ow through said passage.

7. A hydraulically controlled air leg comprising a main air cylinderbarrel having a rear end, a blind end cap thereon, a forward end, and arod end cap on said rear end, a tubular air piston rod extending throughsaid rod end cap into said barrel, an air piston yfixed to said pistonrod in said barrel, a hydraulic piston rod axially arranged in said airpiston rod and having one end fixed to said blind end cap, a hydraulicpiston reciprocally mounted on said hydraulic piston rod, said hydraulicpiston rod having a seat engageable by said hydraulic piston, meansurging said hydraulic piston into seated position, a floating oil`reservoir cover in said air piston rod forwarding of said hydraulicpiston, said air piston rod having therein an air inlet chamberforwardly of said reservoir cover, a forward oil chamber between saidreservoir cover and said hydraulic piston, and a rear oil chamberbetween said hydraulic piston and said air piston, means forming arestricted passageway extending through said hydraulic piston andproviding controlled communication between said forward and rear oilchambers, said hydraulic piston being movable from its seat to establishsubstantially unrestricted communication between said forward andrearward oil chambers, said barrel having therein a main air chamberbetween said air piston and said blind end capand a forward air chamberbetween said air piston and said rod end cap, means forming an airpassage leading from said air inlet chamber to said main air chamber,and a relief valve-controlled air passage leading from said forward airchamber, including a valve-controlled air passage extending through saidair piston from said main air chamber to said forward air chamber.

8. A hydraulically controlled air leg as defined in claim 7, includingan air passage extending through said air piston from said main airchamber to said forward air chamber, a valve in said passage, a springurging said valve into open position, said valve being movable to closedposition in response to air pressure in said main valve chamber.

9. A hydraulically controlled air leg as defined in claim 1, said airpiston rod having an air inlet chamber, said barrel having a main airchamber on one side of said air piston and a forward air chamber on theother side of said air piston, said floating cover dening one wall ofsaid air inlet chamber and separating said forward hydraulic iiuidchamber and said air inlet chamber, means forming an air passagewayleading from said air inlet chamber to said main air chamber, meansforming an air passage leading through said air piston from said mainair chamber to said forward air chamber, a valve axially movable on saidhydraulic piston rod and having a first position closing said airpassage and a second position opening said air passage, said valvehaving a face defining a wall of said rear hydraulic fluid chamber, saidvalve being movable to said second position in response to hydraulic uidpressure in said hydraulic fluid chambers transmitted by air pressure insaid air inlet chamber on said floating cover.

10. A hydraulically controlled air leg as defined in claim l, saidbarrel having a main air chamber on one side of said air piston and aforward air chamber on the other side of said air piston, a valve bodymounted in said barrel adjoining said main air chamber, a valvereciprocally mounted in said body and having therein a first chambercommunicating with said main air chamber and an exhaust chambercommunicating with atmosphere, said first chamber having a pair of portsand said exhaust chamber having a port leadingv externally of saidvalve, said valve body having a first port and a passageway leading tosaid main air chamber and a second port and a pssageway leading to saidforward air chamber, said valve having a first position placing saidexhaust chamber port in registry with said first port to exhaust saidmain air chamber to atmosphere, and a second position placing saidexhaust chamber port out of registry with said first port and inregistry with said second port to exhaust said forward air chamber toatmosphere, and a spring acting upon one face of said valve to urge itin one direction towards said first position, said valve having anopposite face exposed to air pressure in said main air chamber formovement thereby in the opposite direction towards said second position.

1l. A hydraulically controlled air leg as defined in claim l0, includinga check valve in said first chamber controlling communication therefromto said main air chamber.

l2. A hydraulically controlled air leg as defined in claim l0, includinga plastic composition liner mounted in said valve body, said valve beingslidably mounted in said liner, said valve having a plurality ofcircumferentially extending annular grooves each communicating with oneof said ports, said liner having a plurality of series of radiallyextending ports, each said series communicating with one of saidpassageway and arranged for communication with one of said annulargrooves.

13. A hydraulically controlled air leg as dened in claim l0, includinglatch means defining said second position of said valve, said latchmeans being releasable in response to a predetermined degree of airpressure on said valve.

14. A hydraulically controlled air leg as defined in claim l0, includinga housing for said spring reciprocally mounted in said valve body andengaged by said valve to compress said spring, and a spring-loadeddetent engaging said housing, said housing having a recess for receptionof said spring to define said second position of said valve.

15. A hydraulically controlled air leg comprising a main cylinderbarrel, an air piston rod extending axially into said barrel and havingrear and forward hydraulic fluid chambers therein, an air piston fixedto said piston rod in said barrel and providing therein a main airchamber on one side of said air piston and a forward air chamber on theother side of said piston, a tube concentrically arranged within saidair piston rod in radially spaced relation thereto to provide an annularair passage therebetween, a hydraulic piston rod fixed to and axiallyarranged in said barrel, said hydraulic piston rod extending throughsaid air piston, a floating cover in said tube defining one end of saidforward hydraulic fluid chamber, a hydraulic piston on said hydraulicpiston rod, said hydraulic piston separating said rear and forwardhydraulic fluid chambers, means providing a hydraulic fluid flow passagethrough said hydraulic piston from one of said hydraulic fluid chambersto the other, and means controlling iiuid flow through said hydrauliciiuid flow passage, said annular air passage having a port communicatingwith said forward air chamber and an air inlet and outlet port, saidmain air chamber having an air inlet and outlet port.

16. A hydraulically controlled air leg comprising a main cylinderbarrel, a hollow air piston rod extending axially into said barrel, anair piston fixed to said piston rod in said barrel and providing thereinan air chamber on each side of said air piston, a floating hydrauliccartridge in said piston rod and having an external diameter less thanthe internal diameter of said piston rod to provide an air passageextending longitudinally through said piston rod, said cartridgecomprising a tube, a cover closing one end of said tube, and a floatingcover closing the other end of said tube, a hydraulic piston rod ixedlymounted Within said barrel and extending axially through said iirstcover into said tube, a hydraulic piston carried by said hydraulicpiston rod Within said tube, and defining a hydraulic uid chamber oneach side of said hydraulic piston, means providing a hydraulic uidpassage extending through said hydraulic piston from one of saidhydraulic fluid chambers to the other of said hydraulic uid chambers,said air passage having communication with one of said air chambers, andmeans forming an air supply passage communicating with said air passage.

14 17. A hydraulically controlled air leg as defined in claim 16, saidhydraulic piston having valve means responsive to axial movement of saidtube in each direction and controlling uid ow through said hydraulicfluid passage.

References Cited in the file of this patent UNITED STATES PATENTS2,078,364 Becker Apr. 27, 1937 2,132,519 Slater Oct. 11, 1938 2,193,736Onions Mar. 12, 1940 2,564,790 Orlotf Aug. 21, 1951 2,679,827 PurdueJune 1, 1954 2,813,515 Curtis Nov. 19, 1957 3,055,343 Kurt Sept. 25,1962

1. A HYDRAULICALLY CONTROLLED AIR LEG COMPRISING A MAIN CYLINDER BARREL,AN AIR PISTON ROD EXTENDING AXIALLY INTO SAID BARREL AND HAVING REAR ANDFORWARD HYDRAULIC FLUID CHAMBERS THEREIN, AN AIR PISTON FIXED TO SAIDPISTON ROD IN SAID BARREL, A HYDRAULIC PISTON ROD AXIALLY ARRANGED INSAID BARREL AND FIXEDLY CONNECTED THERETO, SAID HYDRAULIC PISTON RODEXTENDING THROUGH SAID AIR PISTON, A FLOATING COVER IN SAID AIR PISTONROD DEFINING ONE END OF SAID FORWARD HYDRAULIC FLUID CHAMBER, AHYDRAULIC PISTON ON SAID HYDRAULIC PISTON ROD, SAID HYDRAULIC FLUIDCHAMBERS, AND MEANS PROVIDING AN OIL FLOW PASSAGE THROUGH SAID HYDRAULICPISTON FROM ONE OF SAID CHAMBERS TO THE OTHER.